Several different types of pumps are used by medical personnel to infuse drugs into patients. Of these, cassette infusion pumps are often preferred because they provide a more accurately controlled rate and volume of drug infusion than other types of infusion pumps. A cassette pump employs a disposable plastic cassette disposed in the line extending between a drug reservoir and the patient's body. The cassette is inserted into an appropriate receptacle of a pump chassis. The pump chassis provides the driving force that pumps fluid through the cassette and typically includes a microprocessor control programmed to deliver a selected volume of fluid to the patient at a selected rate of flow. In addition, the pump chassis may include one or more pressure sensors and air bubble sensors used to monitor the drug infusion process to protect against potential problems that may arise during the drug delivery.
In prior art designs for the pump chassis, it is common practice to latch a pumping cassette into a receptacle by closing a door over the cassette. When thus closed, the door retains the cassette in a predefined position within the pump chassis. However, the door, its hinges, and its latch tends to add considerable weight and bulk that is a disadvantage in an ambulatory drug infusion system. In at least one prior design for an ambulatory pump chassis, retention of the cassette in its receptacle has required following a four-step process. This prior design employs a sliding cover over the cassette receptacle, with a separate latch for retaining the cassette in the receptacle. Accordingly, to load a cassette into this pump, it is necessary to: (1) press the slide into its open position, (2) open the latch, (3) insert the cassette into its receptacle, and (4) close the slide over the cassette. A corresponding four-step process is also required to remove a cassette from the pump chassis in this pump. Clearly, such a procedure is likely to be considered excessively time consuming and complex when it must be repeated each time that a cassette is engaged in the pump chassis to deliver a drug to a patient.
Thus, it would be preferable to provide a much simpler mechanism for engaging a pumping cassette in a predefined position so that the pump chassis can properly drive the cassette and can monitor pressure and detect any air bubbles in the fluid being administered to a patient. It would be preferable to eliminate any door or slide covering the cassette and to provide a mechanism for unlatching the cassette from the pump chassis with the push of a button. The prior art does not disclose any such mechanism for latching and/or unlatching a cassette in a pump chassis.